and lastly, four years you count or you don't want. there is no information about where or when the photos were taken. his wife says it's not clear why they were sent. >> i have no idea what purpose they serve, which is why we held onto them so long. i'm releasing them now to make sure that people are aware that he is still in someone's custody, and i believe it's the iranians and has not been released, and it is almost six years an is still not home with his family. >> reporter: u.s. officials also believe that he is being held by iran. he was working as a private investigator and last seen on an iranian island before he disappeared. u.s. investigators say the expertise used to cover up the track of the email sender looks like the work of professionals, such as iran's intelligence and security service. iran meanwhile has repeatedly denied any involvement in the abduction. his former employer the f.b.i. has posted a million dollar reward for information leading to his return. they say the agency is quote, doing all we can to bring bob